SEC Document

The following discussion of the terms of the notes supplements the description of the general terms and provisions of the debt securities
contained in the accompanying prospectus and identifies any general terms and provisions described in the accompanying prospectus that will not apply to the notes. Certain terms used but not defined in this prospectus supplement have the meanings
specified in the accompanying prospectus.

General

The aggregate principal amount of the notes will initially be $300 million, and the notes will mature on January 15, 2048. The notes
will be issued only in fully registered form without coupons, in minimum denominations of $2,000 with integral multiples of $1,000 in excess thereof.

We will issue the notes under an indenture, dated as of April 8, 2014, as supplemented and amended by an officers certificate to be
dated as of the issue date of the notes, between Wells Fargo Bank, National Association, as Trustee, and us (the indenture). You should read the accompanying prospectus for a general discussion of the terms and provisions of the
indenture. We may, from time to time, without giving notice to or seeking the consent of the holders of the notes, issue additional debt securities having the same terms (except for the issue date, the public offering price and the first interest
payment due date) and ranking equally and ratably with the notes offered hereby. Any additional securities having such similar terms, together with the notes offered hereby will constitute a single series of debt securities under the indenture. The
indenture does not limit the amount of debt that may be issued by us or our subsidiaries under the indenture or otherwise.

We do not
intend to apply for the listing of the notes on any securities exchange or for the quotation of the notes in any dealer quotation system.

Ranking

The notes will
be our senior unsecured obligations and will rank equally with all of our other existing and future senior unsecured indebtedness. The notes will be effectively subordinated to all of our existing and future secured indebtedness to the extent of the
assets securing that indebtedness. In addition, we are structured as a holding company, and we conduct all of our business operations through our subsidiaries. The notes will be structurally subordinated to all existing and future indebtedness and
other liabilities and commitments of our subsidiaries to the extent of the assets of such subsidiaries, which are distinct legal entities having no obligation to pay any amounts pursuant to the notes or to make funds available for such purposes.

As of August 31, 2017, our total consolidated indebtedness was $2,122.3 million, of which an aggregate of $0.5 million was
secured indebtedness of our subsidiaries and our subsidiaries had $92.3 million of indebtedness, $87.9 million of which is related to subsidiary borrowings under our revolving credit facility (guaranteed by the Company) and
$4.4 million of which is related to various mortgages, lines of credit or notes payable held by our subsidiaries). After giving effect to the issuance of the notes and the use of proceeds therefrom, our total consolidated indebtedness would
have been $2,172.6 million.

Interest

The notes will bear interest at a rate of 4.250% per year from the most recent interest payment date on which we paid or provided for
interest on the notes. The interest payment dates for the notes are each January 15 and July 15 and regular record dates for interest payments are January 1 and July 1. The first interest payment will be
on July 15, 2018 and will include accrued interest from, and including, December 20, 2017.

Interest will be computed and
paid on the basis of a 360-day year consisting of twelve 30-day months. See Description of Debt SecuritiesGeneral in the accompanying prospectus.

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About RPM

RPM International Inc. (NYSE: RPM) owns subsidiaries that are world leaders in coatings, sealants, building materials and related services. From homes to precious landmarks worldwide, their brands are trusted by consumers and professionals alike to protect, improve and beautify. Among its leading consumer brands are Rust-Oleum, DAP and Zinsser.